1. Field of the Invention
The present invention relates to a web processing system for slitting a wider web into a plurality of narrower webs for use as photographic photosensitive webs (films), and winding the narrower webs.
2. Description of the Related Art
Generally, web processing systems have a web slitting device for slitting a wider web of film, paper, metal foil, or the like into a plurality of narrower webs, and a winding device for winding the narrower webs.
The web processing systems also have a side edge delivery device for delivering side edges that are severed off the wider web when it is slit. Heretofore, the side edge delivery device comprises delivery rollers and nip rollers for nipping and delivering the side edges. For details, reference should be made to Japanese laid-open patent publication No. 8-257990, for example.
When the wider web is slit into the narrower webs by rotary blades, it is necessary for the side edge delivery device to apply a predetermined level of tension to the side edges in order to give highly accurate transverse dimensions to the narrower webs.
If the side edges were not tensioned or were tensioned excessively, then the wider web that reaches the rotary blades would be flexed, resulting in a reduction in the accuracy of the transverse dimensions of the narrower webs.
One conventional side edge delivery device which is capable of applying tension to side edges (hereinafter referred to as “conventional side edge delivery device”) is disclosed in Japanese laid-open patent publication No. 10-6126, for example.
The conventional side edge delivery device comprises nip rollers that are pressed against delivery rollers under a constant pressure by cylinders, and motors operatively coupled to the delivery rollers by respective clutches. The clutches are supplied with exciting currents that are variable to apply a desired tension to the side edges.
As described above, for imparting a desired tension to the side edges, the cylinders are connected to the respective nip rollers and the clutches are operatively coupled between the delivery rollers and the motors. However, the clutches are responsible for an increase in the manufacturing cost of the conventional side edge delivery device.
The motors are rotated at a constant speed at all times, and the exciting currents of the clutches are controlled to set the side edge tension to a desired value. Therefore, while the slitting process is being suspended, the clutches slip at an increased speed, and hence tend to generate an increased amount of heat.
Winding devices that are in practical use for winding narrow webs having a small thickness ranging from 10 to 20 μm, e.g., ½-inch and 8 mm magnetic tapes, have a tension fluctuation ratio of ±5% or less.
However, winding devices for winding wide webs having a large thickness ranging from 100 to 150 μm, e.g., photographic photosensitive webs (films), with a low tension fluctuation ratio, have not yet been developed in the art.
As shown in FIG. 15 of the accompanying drawings, a conventional film winding device 500 comprises a drive shaft 504 with an air tube 502 disposed therein, and a winding core 512 rotatably mounted on the drive shaft 504 by bearings 506, 508, for winding a film 510 therearound. The conventional film winding device 500 also includes a displacement transmitting member 516 disposed around the air tube 502 within the winding core 512 and having a felt pad 514 mounted on a radially outer surface thereof.
When compressed air is introduced into the air tube 502, the air tube 502 is expanded to displace the displacement transmitting member 516 radially outwardly for thereby pressing the felt pad 514 against an inner wall surface of the winding core 512 for slipping contact therewith.
The torque that is generated when the felt pad 512 slips against the winding core 512 is used as a tension applied to the film 510 when the film 510 is wound around the winding core 512.
However, the conventional film winding device 500 is disadvantageous in that the tension applied to the film 510 is not stable and the tension fluctuation ratio can only be lowered to about ±15% even if the conventional film winding device 500 is well conditioned. Furthermore, the conventional film winding device 500 is unable to produce large tension because of its principles of operation. The maximum tension that can be generated by the conventional film winding device 500 is about 10 N at the most, when the width of a narrow web to be wound is 35 mm, for example. If more tension is produced, then the film 510 that is wound tends to be deformed due to the heat. Moreover, since the air tube 502 is mounted in the drive shaft 504 and the felt pad 514 is attached to the radially outer surface of the displacement transmitting member 516, the conventional film winding device 500 is complex in structure and its maintenance needs to be carried out by skillful operators.